This invention relates to a generally to systems and methods for suctioning liquids and particularly to a system and a method for suctioning blood that reduces the potential for trauma to blood and to cardiac tissue during surgical procedures.
Blood collection during surgery is a commonplace and necessary procedure. Blood collection is typically performed to remove blood from the operating or surgical field to provide the surgeon with a clear view of the body and its organs. In addition, during a procedure such as an open heart surgery, blood is also collected to remove blood from the left ventricle. Blood removed from either location is often referred to as xe2x80x9csurgical bloodxe2x80x9d.
The standard blood collection device is a roller pump operated at a constant speed or rotation rate to provide suction within various xe2x80x9csuctionxe2x80x9d or xe2x80x9csuckerxe2x80x9d lines applied to the surgical field to collect the blood. These roller pumps lack the ability to detect either high levels of pressure or high levels of suction. The pumps also have no method of or apparatus for detecting the relative amounts of air and liquid in the lines.
Blood is removed from the operating field by using a roller pump to drive or apply a vacuum to a suckerxe2x80x94line typically plastic tubingxe2x80x94having a sucker tip on its distal end. To increase the volume of blood and the quickness with which the blood can be removed from the operating field, the perfusionist will increase the speed of the roller pump and thus will increase the amount of suction at the sucker tip on the distal end of the sucker line. Conversely, reducing the roller pump speed will reduce the suction and the speed with which a certain volume of blood can.be removed from the operating field.
The use of standard roller pumps is known to have several problems associated therewith. First, currently used systems for blood collection typically operate at high negative pressures independently of the presence or absence of gas within the lines. Thus, even though there may be little blood in the lines or tubes and a great amount of air or gas, the collection device will continue to suck at a high pressure. Suction of blood mixed with air can cause significantly greater hemolysis than suction of blood alone. Thus, increasing the roller pump speed to suck a larger volume of blood more quickly is likely to bring more air into the sucker line to react with the blood in the line, thereby causing more damage to the blood. Using current technology roller pumps for blood removal thus strikes a compromise between a preferred suction level for the rapid removal of blood from the operating field and the possibility of damage to the blood. That is, if the perfusionist reduces the roller pump speed, then the surgeon will have to take longer to remove any large pool of blood in the operating field, thereby lengthening the operation and the increasing the possibility of less desirable outcomes to the surgery. Increasing the speed to reduce the time spent in surgery, however, can result in damage to the blood.
Second, current devices can allow the blood to stagnate within the sucker lines, which can lead to hemolysis also. This occurs because the current devices operate continuously at high pressures. Thus, to avoid damage to tissue from the continuous negative pressure in the sucker tip, the suction is either turned off or the sucker tip is removed from the operating field, allowing it to draw air directly into the sucker line. If the suction is turned off, then there is no longer any negative pressure available to move the blood in the line further therethrough, thus allowing the blood to stagnate.
Third, most of the devices, as noted, use roller pumps. These devices compress blood filled tubing to pump the blood, which can destroy or damage the blood cells.
Fourth, as noted, the devices are used at high pressures regardless of the presence of air in the collection tubes. When the sucker tip or cannula contacts tissue or an all blood solution, the negative pressure increases suddenly. The increase in negative pressure creates sheer and traumatizes the blood at the collection site, that is, it increases the risk of hemolysis.
Fifth, removing blood from the left ventricle with too high of a suction level can damage the heart. Currently, cardiac damage is hopefully avoided through the utilization of a three-way valve in the suction line that opens to air at a predetermined trigger level, such as when the suction level reaches about 180 mm Hg. When the trigger pressure level is reached, the valve opens to allow air into the line and to prevent the suction level from generally exceeding the trigger level. The three-way valve just described is not a complete remedy to the problem of too much suction, however, since the air introduction, while reducing the potential for damage to the heart, creates a direct air-blood interface that can potentially damage the blood.
Systems that employ suction to remove surgical blood from a surgical field include those disclosed in the following US Patents, all of which are incorporated into this application by reference in their entireties: U.S. Pat. No. 3,834,388 (Sauer); U.S. Pat. No. 4,062,360 (Bentley); U.S. Pat. No. 4,205,677 (Engstrom); U.S. Pat. No. 4,416,658 (Numazawa et al.); U.S. Pat. No. 4,435,170 (Laszczower); U.S. Pat. No. 4,540,399 (Litzie et al.); U.S. Pat. No. 4,599,093 (Steg, Jr); U.S. Pat. No. 4,692,097 (Siposs); U.S. Pat. No. 4,706,687 (Rogers et al.); U.S. Pat. No. 4,735,606 (Davison); U.S. Pat. No. 4,828,543 (Weiss et al.); U.S. Pat. No. 4,838,281 (Rogers et al.); U.S. Pat. No. 4,976,682 (Lane et al.); U.S. Pat. No. 5,055,198 (Shettigar); U.S. Pat. No. 5,195,995 (Walker); U.S. Pat. No. 5,354,268 (Peterson et al.); U.S. Pat. No. 5,385,540 (Abbott et al.); U.S. Pat. No. 5,401,255 (Sutherland et al.); U.S. Pat. No. 5,411,472 (Steg, Jr. et al.); U.S. Pat. No. 5,423,738 (Robinson et al.); U.S. Pat. No. 5,441,482 (Clague et al.); U.S. Pat. No. 5,520,652 (Peterson); U.S. Pat. No. 5,531,712 (Malcolm et al.); U.S. Pat. No. 5,645,531 (Thompson et al.); U.S. Pat. No. 5,573,502 (LeCocq et al.); U.S. Pat. No. 5,571,081 (Adhoute); and U.S. Pat. No. 5,588,816 (Abbott et al.).
It would be desirable to have a system and method for removal of surgical blood that would reduce the potential for damage to the heart and blood during its use. In particular, it would be desirable to have a system and method for removal of surgical blood that would allow the perfusionist or other user to employ continuous suction at a low negative pressure while still satisfying the need for removal of blood in a timely and complete manner.
It is an object of the present invention to provide new and useful systems and methods that are not subject to the foregoing deficiencies.
It is another object of the present invention to provide a system for suctioning blood that is less likely to create damage to either the heart or the blood during use.
It is still another object of the present invention to a new and useful method of suctioning surgical blood that is less likely to create damage to either the heart or the blood during its use.
An automatic control system and methods of automatic control for reducing the blood/air interface for suction from the left ventricle and/or operating field enable the achievement of the foregoing objects of the present invention. A system in accord with the present invention provides continuous suction at a low negative pressure and enables the operator to maintain a constant, predetermined pressure by adjusting the roller pump speed in response to sensed pressures in the sucker line. A system in accord with the present invention will have a pressure sensor or monitor, a pump, and a bubble or air sensor to detect the ratio of air-to-blood in the sucker lines. The system will also have a processing means connected to the pressure sensor, pump, and air sensor for automatically adjusting the pump speed in response to the sensed pressure and/or the sensed air-to-blood ratio, and may have a display and the appropriate manual controls to manually adjust the pump speed also connected to the processing means.
A method in accord with the present invention will provide for the sensing of the pressure and the air-to-blood to blood ratio and adjusting the pump speed in accord therewith so as to continuously maintain a suction level that will be adequate to remove the necessary and desired amount of blood without damage to surrounding tissue. In particular, the system will used sensed air-to-blood ratios to adjust the pump speed to desired levels so as to maintain a continuous suction at low pressure levels, varying the pump speed as needed to do so, as opposed to the single speed, high pressure provided by present day blood collection systems.
The system in accord with the present invention will be operable in one or more modes, such as a manual, automatic, constant vacuum, xe2x80x9cblood comingxe2x80x9d detection, blood/air percentage detection; variations to automatic mode, and may include filtering features.